As is known, the gonadotropic hormones or gonadotropins are hormones stimulating the gonads. In mammals, the gonadotropins are generated by the hypophysis, the placenta, and, as regards pregnant mares, also by the endometrium. The gonadotropic hormones comprise the follicle-stimulating ones (FSH), the luteinizing ones (LH) luteotropine (LTH) and chorionic gonadotropin (HCG). It is known that the biological effects of HCG and LH are similar. It is also known that the urine of pregnant mammals contains chorionic gonadotropin of placental origin and that in women, in the midst of the menstrual cycle, the urine contains LH of hypophyseal origin of which the action causes ovulation and formation of yellow body. It is further known that the urine of the female in the pre-menopause period, that is, in the case of incipient menopause, contains gonadotropins of hypophyseal origin.
The presence of chorionic gonadotropin of placental origin in the urine constitutes one of the early diagnostic means for pregnancy. This is the reason reagents allowing early diagnosis of pregnancy were developed.
These reagents in essence are substrates on which are adsorbed antigens consisting of chorionic gonadotropins (HCG) and chorionic gonadotropin antisera; the reaction between the HCG antigen and the antiserum on the substrate results in a clear, yellow precipitate homogeneous in nature, i.e. the agglutinate. When there is excess of free HCG in the reactive medium -- for instance when the HCG is obtained from the urine of the pregnant female -- there will be no reaction as above, it being inhibited by the presence of HCG in the urine, and no agglutinate will be formed.
When the substrate on which the HCG is adsorbed consists of suitably treated erythrocytes and when there is no erythrocyte-antiserum reaction, and no agglutinate is formed, the erythrocytes will settle at the bottom of the test tube as a dark-brown ring. This reaction, which is known as the WIDE & GEMZELL reaction, was described in ACTA ENDOCRINOL, 35, 261 (1960); it was applied in French Pat. Nos. 1,299,171 and 1,343,189 under the name of ORGANON N.V. Also please see French Pat. No. 1,516,630 (U.S. equivalent U.S. Pat. No. 3,548,051) and French Pat. No. 1,186,147.
When the substrate used consists of a synthetic polymer as described in French Pat. Nos. 1,322,869 and 1,411,279 under the name of ORTHO PHARMACEUTICAL CORP., wherein the antigen/antiserum reaction is inhibited by the presence of HCG in the urine being tested, there will be no agglutination reaction.
However, the reagents described in the patents above are so sensitive that the antigen/antiserum reaction will be inhibited not only when the urine being tested contains chorionic gonadotropin from a pregnant subject, that is, of placental origin, but also when such urine contains gonadotropins of hypophyseal origin as in the cases of incipient menopause and in the middle of the menstrual cycle.